Physical vapor deposition (PVD) plays an important role in today's coating process of mass production. PVD is characterized by a process in which the coating material goes from a condensed phase (also called target source) to a vapor phase in an environment with a high vacuum and high temperature and then back to a thin film condensed on a substrate, the product or material that needs to be coated. Compared to the traditional coating methods such as the electroplating process, PVD coatings are more corrosion resistant and durable. In addition, it could be applied to a more diverse group of substrates and surfaces.
However, maintaining uniformity of the coating thickness has been a challenge during the PVD's deposition process. The method used by the industry for managing the coating thickness is to insert one or multiple shielding masks between the substrate and the evaporation source of the coating material. The placement of the shielding mask in the PVD coating chamber helps the evaporated coating material to distribute and deposit more evenly on the surface of the substrate. The effect of the shielding mask on the coating uniformity greatly relates to the shape of the shielding mask. In order to identify the shielding mask's shape that helps achieve the best result of uniformity, a pilot study must be conducted before proceeding to the mass production. In the case of a long time production process for high end products, the shape of the shielding mask needs to be periodically adjusted and calibrated. However, the shielding mask is usually made by hand before the test run. In order to find the best one that fits the process a large amount of shielding masks with different shapes must be prepared. The preparation and test of the conventional shielding mask is time-consuming. Making fine adjustment on the shape of the shielding mask is very inconvenient if not impossible. This could lead to missing the best shape for a good uniformity result. In addition, the reproducibility of test results is low due to the lack of consistency and repeatability of the manually prepared shielding mask.
Therefore, it is very much needed to have a shielding mask that is designed to be quickly set up in the coating process and whose shape can be easily adjusted or tuned without the remaking of the mask. In the meantime, having specially-designed masks is only halfway done in achieving coating uniformity. A method also needs to be developed so that the on-going status of the coating thickness on the substrate could be monitored in real time and provides feedbacks on how and when masks should be used for maintaining uniformity during the deposition process. In this way, appropriate masks would be chosen to either facilitate or reduce the deposition of coating materials on a certain surface area of the substrate and the deposition process could be adjusted accordingly for the next layer's coating.